Surface Modification of Natural Mordenite and Its Application in Removal of Heavy Metals from Aqueous Solution

Abstract

BACKGROUND Natural mordenite is widely used as a green and cheap porous material to remove heavy metals in environmental treatment. Currently, the removal rate of heavy metals by natural zeolites is from 60% to 90%, and improving its removal efficiency has been a hot topic. OBJECTIVES To reconstruct and modify natural mordenite by tetraethyl orthosilicate, and determine its effect on the removal of heavy metals in water. METHODS The morphology and structure of the modified mordenites were characterized by TEM, XRD and BET. RESULTS The SiO2 hydrolyzed by tetraethyl orthosilicate can be combined with natural mordenite to form a new 'SiO2/mordenite'. The surface of the original mordenite is coated with the pore structure of the new nano-SiO2 without damaging the porous structure of the original mordenite. The modified mordenite combines the advantages of natural mordenite and nano-SiO2 pore structure, enhancing the adsorption of heavy metal ions. The highest adsorption rate of modified mordenite for Pb2+, Cd2+, Zn2+, and Mn2+ was 99.3%, 97.1%, 98.3%, and 97.0%, respectively. The modified mordenites were minimally desorbed during the entire process and have stable performance. Considering the cost and the appropriate adsorption rate, the best dosage of adsorption efficiency is selected. The optimal dosage of Pb2+, Cd2+, Zn2+ and Mn2+ solutions for the initial concentration of 10 mg/L is 0.5, 2, 2 and 5 g/L, respectively. It can provide a reference for a pilot experiment and scale applications. CONCLUSIONS Compared with roasting, acid, alkali, salt and organic modification, this modification method has a high adsorption rate for a variety of heavy metals, and shows the advantages of simple operation, low cost and environmental friendliness, making it a good application prospect.

Keywords

• natural mordenites
• silica
• surface modification
• heavy metals
• adsorption